Conventional loudspeaker enclosures containing one or more loudspeakers are subjected to parasitic vibration due to the pressure oscillations generated by the loudspeakers, in particular the loudspeakers for generating base and midfrequency sound. These pressure oscillations act on the walls of the enclosure and cause them to vibrate. In addition, they are multiply reflected on the walls and this gives rise to distortion and coloration in the sound, thereby degrading the quality of music or sound reproduction.
Various solutions have been proposed for increasing sound absorption and reducing sound reflection at the walls of the enclosure.
One of these solutions consists in constructing double-walled enclosures and in filling the space between the two walls with a dense powder material, which is generally sand.
This solution has had to be abandonned since it is expensive due to the fact that two enclosures must be made and the sand must be as highly compressed as possible in the space between them. Further, under the effect of vibration, sand tends to compact, thereby creating voids which may form resonating cavities. Finally, the sand used is often damp, and dampness may give rise to mold which attacks the walls of the enclosure.
Other solutions consist in lining the inside faces of the enclosure walls with fibrous padding made of glass or rock wool, or felt, or "hush" cloth; however sound absorption due to such padding is relatively low, particularly for base sound.
Another problem encountered in loudspeaker enclosures stems from the fact that interference takes place in the inside space behind the loudspeakers between the pressure reflected by the walls and waves due to the displacements of the backs of the loudspeaker cones and the tuning ports.
Some manufacturers have made enclosures which include, behind the loudspeakers, a perforated wall or labyrint constituted by a wooden lattice delimiting cells which are lined with fibrous material.
An object of the present invention is to provide high fidelity loudspeaker enclosures having very good sound reproduction qualities due to novel acoustic screens placed against the inside faces of the walls.
Another object of the invention is to further improve the quality of reproduction by enclosures containing said acoustic screens by means of absorbent blocks which are placed behind the loudspeakers.
Loudspeaker enclosures in accordance with the invention are of the type suitable for containing one or more loudspeakers placed in an enclosure.